The Effects of Climate change on World Aquaculture: A - ecasa

151 Pages·2006·3.32 MB·English

The Effects of Climate change on World Aquaculture:
A global perspective

Handisyde N.T., Ross L.G., Badjeck M-C & Allison E.H.,
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Contents:

Executive summary..................................................................................................................5
1. Climate change and global aquaculture.............................................................................5
Outline of global climate change and climate prediction...................................................5
An overview of global aquaculture....................................................................................5
Impacts of climate change on aquaculture production systems.........................................6
2. GIS based assessment of aquaculture related vulnerability to climate change..................6
3. Case study - Bangladesh....................................................................................................7
Introduction........................................................................................................................7
The physical geography, climate and weather of Bangladesh...........................................7
Current state of aquaculture in Bangladesh........................................................................8
Future potential for aquaculture in Bangladesh.................................................................8
Potential future climate change in Bangladesh..................................................................8
Summary – vulnerability of aquaculture in Bangladesh and potential adaptation.............9
4. Conclusions........................................................................................................................9
1. Climate change and global aquaculture...........................................................................11
Outline of global climate change.........................................................................................11
Climate prediction................................................................................................................13
Models and scenarios.......................................................................................................13
Strengths, weaknesses and uncertainties in relation to climate models and prediction13
Predicted climate changes................................................................................................14
Temperature.................................................................................................................14
Precipitation.................................................................................................................15
Sea level rise.................................................................................................................15
Extreme events.............................................................................................................17
Climate variability........................................................................................................17
Ocean currents and circulation.....................................................................................19
An overview of global aquaculture......................................................................................20
Production systems and trends.........................................................................................20
Overview of the significance of the aquaculture industry to livelihoods.....................23
Aquaculture in the coming decades.................................................................................24
Impacts of climate change on aquaculture production systems: a review...........................28
Impacts on aquaculture production..................................................................................29
Impacts on aquaculture dependant livelihoods................................................................35
Changes in natural capital............................................................................................36
Impacts on physical capital and the influence of financial capital...............................37
Reduced human capital and impacts on social capital.................................................38
Indirect impacts - the influence of capture fisheries........................................................39
Fishmeal and fish oil....................................................................................................41
The Peruvian fishmeal industry as an example............................................................45
2. GIS based assessment of aquaculture related vulnerability to climate change............48
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Introduction..........................................................................................................................48
Spatial and temporal scales..................................................................................................51
Model construction and presentation...................................................................................52
Reclassification................................................................................................................52
Layer combination............................................................................................................52
Weighting of components – use of expert opinion..........................................................53
Evaluation and analysis of questionnaires - assigning of weights used in the vulnerability
model................................................................................................................................54
Data not incorporated in the main model.........................................................................57
Sensitivity sub-model...........................................................................................................58
Outputs.............................................................................................................................60
Layer 1: Sensitivity (Fig 2.4).......................................................................................60
Layer 2: Sensitivity - food security (Fig. 2.5)..............................................................62
Layer 3: Aquaculture production value as % of GDP (Fig 2.6)...................................64
Layer 4: Sensitivity - freshwater aquaculture (Fig 2.7)...............................................64
Layer 5: Sensitivity - brackish water aquaculture (Fig 2.8).........................................66
Layer 6: Sensitivity – mariculture (Fig 2.9).................................................................68
Exposure sub-model.............................................................................................................70
Climate models and scenarios used to provide data.........................................................70
Outputs.............................................................................................................................73
Layer 7: Exposure SRES A2 (Fig 2.10).......................................................................73
Layer 8: Exposure – precipitation change SRES A2 (Fig 2.11)..................................75
Layer 9: Exposure - precipitation change SRES A2 reversed (figure 2.12)................76
Layer 10: Exposure – population density SRES A2 (Fig 2.13)...................................78
Temperature change.....................................................................................................79
Exposure to extreme climatic events sub-model..................................................................79
Outputs.............................................................................................................................81
Layer 11: Cyclone risk (Fig. 2.15)...............................................................................81
Layer 12: Flood risk (Fig. 2.16)...................................................................................81
Layer 13: Drought risk (Fig. 2.17)...............................................................................82
Layer 14: Extreme events (Fig. 2.18)...........................................................................82
Adaptive capacity sub-model...............................................................................................84
Outputs.............................................................................................................................88
Layer 15: Adaptive capacity (Fig 2.19).......................................................................88
Vulnerability.........................................................................................................................89
Outputs.............................................................................................................................90
Layer 16: Vulnerability (figure 2.20)...........................................................................90
Layer 17: Vulnerability - food security (Fig. 2.21)......................................................92
Layer 18: Vulnerability - economic importance of aquaculture (Fig. 2.22)...............93
Layer 19: Vulnerability - adaptive capacity emphasis (Fig. 2.23)...............................95
Layer 20: Vulnerability of freshwater aquaculture to flooding (Fig. 2.24)..................96
Layer 21: Vulnerability of freshwater aquaculture to drought (Fig. 2.25)...................98
Layer 22: Vulnerability of brackish water aquaculture to cyclone (Fig. 2.26)............99
Layer 23: Vulnerability of mariculture to cyclone (figure 2.27)................................101
Vulnerability assessment - summary..................................................................................102
3. Case study - Bangladesh..................................................................................................104
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Introduction........................................................................................................................104
The physical geography, climate and weather of Bangladesh...........................................105
Current weather and climate..........................................................................................106
Flooding.........................................................................................................................107
Current State of Aquaculture in Bangladesh......................................................................113
Future potential for aquaculture in Bangladesh.................................................................118
Potential future climate change in Bangladesh and its impacts on aquaculture.................121
Sea level rise...................................................................................................................121
Extreme events - cyclone and storm surge.....................................................................125
Temperature change.......................................................................................................125
Precipitation change.......................................................................................................128
Summary - vulnerability of aquaculture in Bangladesh and potential adaptation.............131
4. Summary and conclusions...............................................................................................137
References:............................................................................................................................140

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Executive summary

1. Climate change and global aquaculture

Outline of global climate change and climate prediction

• It is now widely accepted that observed changes in the earth’s climate are at least in
part a result of human activities.
• Models for future climate prediction are continually growing in sophistication with the
current generation of General Circulation Models linking both ocean and atmosphere
components. The resolution of global climate models is relatively low and considering
their theoretical nature they are better suited for predicting long term changes in
variables such as temperature and precipitation over larger areas than more localized
and variable phenomena such as cyclones.
• Temperature is predicted to increase more at higher latitudes compared with equatorial
areas. Maximum and minimum temperatures at a given point will vary and there may
be an increase or decrease in the range of temperatures seen at the diurnal, seasonal
and inter-annual time scales.
• As a global average precipitation levels are predicted to increase although southern
Africa, Australia and Central America will most likely see a decrease. Changes in
seasonal variation will also be important and may lengthen or shorten growing seasons
in relation to water availability or increase the risk of flood damage at certain times of
year.
• Mean sea level is predicted to increase between 10 and 90cm during the 21st century
with most predictions falling within the 30 to 50cm range although some uncertainty
remains in relation to land based ice in Antarctica and Greenland.
• Changes in climate variability and extreme events are considered harder to predict
although increases in the intensity of precipitation events, risk of drought and peak
cyclone wind intensities are considered likely in some areas.
• Changes in ocean currents as well as having a substantial influence on the worlds
climate may have significant direct effects on aquaculture through changes in
temperature, primary productivity and hence food availability, and the distribution of
disease, toxic algae blooms and predators.

An overview of global aquaculture
• The global aquaculture industry in continuing to grow, accounting for an increasing
share of total fisheries production.
• Asia and particularly China accounts for the majority of the worlds aquaculture
production.
• While aquaculture plays an important role in the livelihoods of people from a wide
range of areas it is again Asia the greatest numbers can be seen. There are an estimated
9.5 million aquaculturists in Asia and it is likely that many more people will be
involved in supplying a range of goods and services to the sector.
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• Although the average rate of growth in the aquaculture sector appears to have slowed
in recent years compared with the rapid growth seen during the 80’s and 90’s,
continued expansion is predicted for the coming decades as a result of an increasing
demand for fish and the limited production capacity of capture fisheries.
• As a result of economic pressures and the increased development and spread of
aquaculture technologies, it seems likely that a general trend towards more intensive
culture practices will occur.

Impacts of climate change on aquaculture production systems
• Climate change impacts on aquaculture are considered in the current study as either
direct e.g. changes in water availability, temperature or damage by extreme climatic
events, or indirect such as in the case of increased fishmeal costs and its consequences
for aquaculture feeds.
• Potential direct impacts on aquaculture are outlined here in table 1.7.
• The particular sensitivities of aquaculture related livelihoods to different aspects of
climate change will be linked to the type, scale and intensity of aquaculture taking
place as well as the environment in which it is being conducted. There has been a
considerable amount of work focusing on the different aspects of aquaculture
dependant livelihoods, but little that deals directly with the potential effects of climate
change. The sustainable livelihoods approach can be useful in assessing how climate
change may impact on the natural, physical, economic, human and social capitals
necessary for aquaculture.

2. GIS based assessment of aquaculture related vulnerability to
climate change

A Geographic Information System (GIS) based model is used to indicate areas where
livelihoods are likely to be vulnerable to climate change impacts on aquaculture. The model
used the concept that vulnerability (V) is a function of exposure to climate change (E),
sensitivity to climate change (S) and adaptive capacity (AC).

V = f (E, S, AC)

The concept of climate trends, such as gradual changes in mean temperature and precipitation
levels, compared with climate shocks, for example; floods and cyclones, is considered
important when assessing potential impact pathways. The categories of fresh, brackish and
salt water culture are used to give some indication as to the location and type of aquaculture
likely to be taking place within a country. It is considered that the type and location of the
aquaculture environment will influence its vulnerability to particular climate related impacts.

The indicators used in the vulnerability model along with its basic structure are shown in
figure 2.1. All layers are reclassified on a scale of 1 – 5 and layer combination is by Multi
Criteria Evaluation (MCE) using weighted linear combination. Different levels of
significance/weightings can be assigned to layers being combined in the sub and main model.
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Decisions regarding weightings were maid by the authors after obtaining a consensus of
expert opinion from a focus group and guided questionnaire.

Eight combinations of component layers are used to assess vulnerability in relation to a range
of issues, culture environments and climate factors. Table 2.23 highlights countries which
score at least 4 out of 5 for at least part of their area under the different combinations.

Asia featured highly in the vulnerability assessment with the large aquaculture producing
countries such as; Bangladesh, Cambodia, China, India, The Philippines and Vietnam
indicated as vulnerable under most of the layer combinations used.

Aquaculture production in Africa as a whole is low when compared to Asia. However many
African countries are considered to have a very low adaptive capacity and are therefore
considered vulnerable in some instances.

A number of Central and South American countries are considered vulnerable with Nicaragua
and Guatemala being the areas of most concern.

3. Case study - Bangladesh

Introduction

Bangladesh is one of the world’s most densely populated countries with nearly half of the 138
million population being considered bellow the poverty line. Bangladesh is recognised as
being very vulnerable to climate change and sea level. Approximately 85% or the countries
poor live in rural areas, and it is estimated that around 61.5% of the countries employed
people are connected to agriculture. With estimates of over 3 million fish farmers aquaculture
is highly significant within Bangladesh both in terms of food security and economic income.

The physical geography, climate and weather of Bangladesh

Bangladesh is an extremely flat and low-lying deltaic country (Fig. 3.1) with a large
proportion of its area comprising of the floodplain of three converging rivers; the Ganges, the
Brahmaputra-Jamuna and the Meghna (GBM river system). Bangladesh experiences a cooler
dry winter period and a summer monsoon season during which it is forced to drain a large
quantity of cross boarder runoff and as a result an average of 20.5% of the country floods
annually. Peoples livelihoods are typically well adapted to the average annual flooding,
however during extreme flood events such as in 1998 up to 70% of the country can be
inundated. Such events are typically associated with synchronisation of peak flow within the
GBM river system and cause widespread damage.

Bangladesh is also vulnerable to cyclones and associated storm surges which can inundate the
flat low lying coastal areas.
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Current state of aquaculture in Bangladesh

Traditionally aquaculture in Bangladesh has taken the form of extensive pond culture of
freshwater fish species such as carp species, and often relied on natural stocking of fish seed
during flood periods. The current trend is towards more intensive methods and deliberate
stocking of select species. A greater range of fish species are now cultured along with high
value crustacean species such as Penaeus monodon and Macrobrachium rosenbergii.

Future potential for aquaculture in Bangladesh

Bangladesh’s population is predicted to expand from its current level of 138 million to
between 190 and 222 million by 2030. Aquaculture has an important potential role in
providing food for this increasing population in a country where malnutrition is currently
common.

There are a large number of nongovernmental organisations within Bangladesh that are
helping to promote aquaculture. It is hoped that through micro credit schemes and provision
of appropriate information and training that poorer people will be able to participate in small
scale aquaculture, providing both additional food and income.

The culture of high value species such as shrimp is seen as having the potential of generate
substantial export earnings and is been promoted.

Potential future climate change in Bangladesh

Sea level rise is a major concern due to the low elevation of much land in Bangladesh with
inundation estimates of 2500 km2 (2%), 8000 km2 (5%) and 14000km2 (10%) for 0.1, 0.3 and
1.0 metre rises respectively.

Increased salination of ground water may alter the range of species that can be cultured at a
given location.

Loss of natural coastal defences may increase the risk from storm surges.

The Bengal delta has a high level of subsidence with an estimated effective sea level (the
combination of actual sea level rise and the subsidence of land) or more than 10mm per year
under current conditions.

Storm surges represent a serious threat to aquaculture in the countries coastal areas. A
relationship between sea surface temperature and cyclone intensity has been suggested.
Estimated maximum surge height under conditions similar to the 1991 cyclone is 7.6m with a
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predicted increase to 9.2m and 11.3m under 2°C and 4°C surface temperature increases
respectively.

Temperature increases within the Bangladesh region are predicted to be greater during the
winter period compared with the summer. Precipitation levels are predicted to be greater
during the summer monsoon period with possible decreases during the winter months. These
predictions suggest a potential increase in the risk of flooding during the monsoon season as
well as a limited water supply during the winter period. The potential for greater variation as
well as a greater likelihood of synchronised peak flow in the major rivers and consequent
increases in flooding should also be considered.

Summary – vulnerability of aquaculture in Bangladesh and potential adaptation

Within Bangladesh sea level rise with its associated land loss and salination of ground water
as well as risk from storm surges and inland flooding would appear to represent the greatest
potential climate related risks to aquaculture. The potential for water shortages during winter
as a result of decreased precipitation combined with an increasing population should also be
considered.

The promotion of suitable culture methods and species within a given area in relation to both
people’s socio economic situation and changing environmental conditions will be important in
helping gain the maximum benefit from aquaculture. Further research should be encouraged
with the following areas seen as especially significant:

• Awareness of latest climate predictions for the Bangladesh area, especially those
involving precipitation regimes, sea level rise and if possible tropical storms.
• Organisation and availability of historic data and research.
• Analysis of site suitability for aquaculture based on:
o Predicted changes in climate and consequent environmental factors: Water
availability, Salinity and temperature.
o Risk from extreme events notably riverine and storm surge floods.
o Social and economic evaluations and predictions.
o Resource availability e.g. Seed, inputs and support networks.
• Continued improvement and development of aquaculture practices for a broad range
of species in order to maximise production where possible.
• Production and distribution of quality seed.
• Cost benefit analysis for a wide range of species and culture methods in relation to
climatic and environmental variables.

4. Conclusions

• The current study provides a strong starting point and a useful guide for further
investigations both at more local level and with a focus on more specific issues.
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• More focused case studies will be very important not only in guiding policy decisions
for the areas concerned, but also for the increased understanding of the ways in which
climate change impacts will take place along with possible adaptive measures to
counter them. It may then be possible to apply the knowledge and working methods
gained from one area to others with similar characteristics.
• Ability to adapt to climate change will be strongly linked to adaptive capacity making
economic predictions an important part of vulnerability assessment.
• The promotion of suitable species and culture methods at a given location in order to
maximise production and profits in the face of a changing climatic, socio economic
and environmental variables will be important. The use of Geographic Information
Systems (GIS) are seen as providing powerful tools in this area.
• The efficient organisation, distribution, and where possible free availability of data
and literature will greatly assist future work and help determine what can be achieved
with the limited time and resources available.

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